Culebra or St John?

Both islands are built around their beaches, and the difference is in how the beaches are laid out. Culebra has one famous strand, Flamenco, with its old naval tanks in the shallows. Around it are smaller beaches near Dewey, such as Tamarindo and Melones, where reefs start a few metres from the shore, and Tortuga Beach on Culebrita, which you reach by water taxi or kayak. Winter swells can roughen the north-facing beaches.

On St John the beaches run in a line along the north shore road, almost all of them inside the park. Trunk Bay has a marked snorkel trail, and turtles graze in the seagrass at Maho and Francis. The quieter, rockier bays are on the south side, around Salt Pond. The best-known St John beaches fill by late morning in winter, so it pays to arrive early.

St John has more choice, almost all of it in Cruz Bay. As well as open-air grills and beach bars, there are West Indian kitchens serving johnnycakes, pâtés, saltfish and stewed goat, and rum punch and painkillers are the local drinks.

Culebra's eating is simpler: a few seafood places and food trucks in Dewey selling mofongo and empanadillas, and menus that get shorter when supplies on the ferry run low. On both islands almost everything is shipped in, and plenty of visitors cook for themselves.

Neither island is a culture trip, but St John gives you more to see. The Annaberg sugar mill overlooks the north shore, Taíno petroglyphs sit beside a pool at the end of the Reef Bay Trail, and at Coral Bay there is an old Moravian church and the fort where the slave revolt of 1733 began. Together they are worth a morning or two.

Culebra's history is more recent and harder to see. The small museum in Dewey's old navy powder magazine tells the story of the decades of bombing practice, and the tanks on Flamenco and the ruined lighthouse on Culebrita are its landmarks.

Sunset at an open-air bar near the Dewey ferry dock is about as late as Culebra goes. Some weekends there is a band, but most of the island is asleep soon after dinner, so it suits a drink after a day in the sea and little more.

Cruz Bay keeps going a little longer. Visitors, boat crews and island residents share its waterfront bars until late evening, and Coral Bay has a couple of easy-going spots of its own. Anyone who wants a later night can take the short ferry to St Thomas, since there are no clubs on either island.

St John's protected land is its main advantage. Most of the island is national park, with steep dry forest, trails down the Reef Bay valley and out to the cliffs of Ram Head, and good snorkelling at Waterlemon Cay and Maho Bay. You can spend a day on the water and the next one on foot.

Culebra's nature is almost all at sea. The Luis Peña marine reserve has some of the healthiest reefs around Puerto Rico, and dive boats go out to walls and wrecks among the cays. Seabirds and nesting turtles use the outer cays and remote beaches, but on land the island is low and scrubby, with only short walks.

From St John, a day out is easy to arrange. Charlotte Amalie on St Thomas, with its Danish streets and fort, is about twenty minutes away by ferry, and day charters go to Jost Van Dyke and The Baths on Virgin Gorda, though the British islands need a passport.

From Culebra, a day out means a boat to the empty cays and Culebrita. Vieques and Fajardo on the main island can be reached, but the journey is too awkward for a simple day trip, so most people stay on the island.

Both islands suit families whose children love the water, and both have almost nothing built for children. On Culebra the strengths are Flamenco's calm shallows and the waist-deep snorkelling at Tamarindo. The drawbacks are limited medical care and a ferry or small-plane crossing that is hard with toddlers.

St John has turtles at Maho in water where a child can stand and an easy first snorkel on the Trunk Bay trail. On the other hand, getting there means a flight, a taxi and a ferry, few beaches have lifeguards, and many villas are up steep hills.

Both islands are about equally awkward to reach, in different ways. Culebra depends on the ferry from Ceiba, which is often full at weekends and does not always run on time, or a small plane from San Juan. On St John you fly into St Thomas, take a taxi to Red Hook and then a short ferry.

On the island, Culebra is easy with shared vans and hired golf carts. St John's switchback roads, driving on the left and full beach car parks in winter make it harder work, although safari taxis run out to the north shore.

St John has more to buy, though only enough for an hour or so: galleries, jewellers and craft such as hook bracelets and painted pottery in Cruz Bay's courtyards near the dock, and the duty-free streets of Charlotte Amalie a ferry ride away. Culebra has a few souvenir shops and local artists in Dewey, and anything you need is best bought before the crossing.

Neither island is cheap, but Culebra costs noticeably less. Its guesthouses, small inns and rentals with kitchens make it easier to cook for yourself, and the biggest extra is usually a golf cart or jeep.

St John's villas and few resorts charge high rates in winter, and ferries, taxis and jeep hire soon add up. The ways to save are the campground at Cinnamon Bay and the lower rates in summer and autumn, which are also the hurricane months.

Culebra's one musical occasion of the year is its patron saint festival, which brings music to Dewey. Apart from that, live music means a band in one of the town's bars on some weekends.

St John's carnival, the St John Festival in early summer, is a much bigger event, with parades, calypso and quelbe music. Through the rest of the year, singer-guitarists and the odd steel pan or reggae band play the waterfront bars in Cruz Bay and Coral Bay. Neither island has a theatre or concert hall.

On Culebra, guesthouse yoga and a handful of independent massage therapists are all there is. The rest of the rest comes from having no big resorts, little traffic and long, empty afternoons.

On St John a therapist will come to your villa, and there are small yoga studios and treatments at the resorts as well. The setting does more of the work, though. With most of the island under park protection, a typical stay is a hillside villa looking over the water, with nights that are quiet apart from the tree frogs.